The type of valve assembly to which the present invention generally relates is familiar to both the brewing and tavern industries. It comprises an annular valve body that is detachably secured in an outwardly projecting neck surrounding an opening in a keg. Cooperating with the valve body to define an annular gas passage is a coaxial annular gas valve member that is movable axially inwardly and outwardly relative to the valve body, from and to a position in which the gas valve member engages a seat on the valve body to seal the gas passage. Coaxially fixed to the annular gas valve member is an elongated siphon tube that projects inwardly from it and defines a liquid passage through which liquid can be forced out of the keg under the pressure of gas admitted through the gas passage. When the valve assembly is not connected with a filling mechanism or a tapping coupler, the liquid passage is sealed at its outer end by a liquid valve member that is biased outwardly into engagement with a seat on the inner periphery of the annular gas valve member. A tapping coupler detachably connectable with this valve assembly holds open the gas and liquid valves and provides for conducting gas from a pressurized source to the gas passage and for conducting liquid from the liquid passage to a tap at which it can be drawn for dispensing.
Keg valve assemblies of the type here under consideration have been the subject of more or less constant inventive and developmental activity for many years, as is evident from the substantial body of patent literature on such devices. This prior activity has focused almost exclusively on those aspects of the valve assembly that relate to its functions as a seal for the keg and as a device cooperable with a tapping coupler for drawing liquid out of the keg. However, little attention has been given to problems posed by such a valve assembly in the filling of a keg in which it is installed, although the brewing industry has for some time been aware of the existence of those problems. Specifically, brewers have found that a keg equipped with a conventional valve assembly must be filled with beer at a very slow rate during the initial stages of the filling operation in order to avoid overcarbonation and foaming of the product and consequent underfilling of the keg. Because of this slow filling rate, the keg filling operation tends to be a bottleneck which limits the output capacity of a brewery. Research has established that the heretofore conventional keg valve assembly is responsible for the restriction on filling rate, but the industry concerned with the manufacture of such assemblies has heretofore been unable to solve the problem.
In preparation for filling, a keg is first washed, rinsed and cooled and is then charged with carbon dioxide gas to purge it of steam and air. From the time it is delivered to the washing stand, through the filling operation, the keg is oriented with its neck lowermost so that the siphon tube projects upward from the valve assembly. At the filling stand the gas and liquid valves of the valve assembly are held open and beer is charged into the keg through the gas passage. Meanwhile, the siphon tube serves as a standpipe through which carbon dioxide leaves the keg as it is displaced by the incoming beer. Filling is automatically terminated as soon as the entry of beer into the siphon tube is detected by a sensor.
With prior keg valve equipment, if beer was delivered into the keg at a high flow rate during the initial stages of filling, it tended to issue from the valve assembly into the keg interior as upwardly directed jets or sprays. These presented large surface areas at which the carbon dioxide in the keg was absorbed. With such overcarbonation and agitation the beer foamed vigorously. Foam would then enter the siphon tube, causing filling to terminate well before the level of unfrothed beer reached the upper end of the siphon tube, and consequently the keg would be underfilled. To prevent such overcarbonation and underfilling, it was necessary to hold the inflow of beer to a very low rate until the keg had been filled to a level well above the valves of the keg valve assembly. From that point jetting and spraying were suppressed by beer already filled into the keg, and the inflow could be increased to the full rate available with the filling equipment. Obviously, the prolonged initial period of low inflow rate played a major role in determining the time required for complete filling of a keg.
A major cause of jetting and spraying at high initial filling rates was the portion of the valve assembly that provides for biasing the annular gas valve member to its closed position. This comprises a coiled expansion spring that surrounds the siphon tube and a spring retainer having a cylindrical wall that surrounds the coiled spring in coaxial, radially spaced relation to it and to the siphon tube. At its axially outer end the spring retainer is coaxially secured to the annular valve body that is seated in the keg neck; at its axially inner end the spring retainer provides a seat or abutment against which the inner end of the coiled spring reacts. The outer end of the coiled spring is of course engaged with the gas valve member to bear axially outwardly against it. The annular gas passage, which is jointly defined by the annular valve body and the annular gas valve member and through which beer enters the valve assembly, opens axially inwardly to the annular space between the cylindrical spring retainer wall and the siphon tube.
Because of the geometry of the gas passage, beer passing out of it into the annular space just mentioned tends to flow mainly along the cylindrical spring retainer wall, especially at high inflow rates. To allow the incoming beer to pass out of that space, there are large holes in the cylindrical wall. Some portion of the incoming beer does in fact pass through those holes at all flow rates, but especially at high flow rates a substantial portion of it continues in axial flow along the cylindrical wall, and with prior valve assemblies it was this axial flow component that mainly gave rise to jets and sprays.
The spring seat at the inner end of the cylindrical spring retainer wall comprises radially inward projections that are usually formed in one piece with the wall itself. In some valve assemblies these projections are relatively large and the spring directly engages them, in others they comprise relatively small tabs that are overlain by a washer-like spring seat member. In those devices wherein the spring seat comprises a washer, there were usually small spaces between it and the cylindrical wall through which beer tended to issue in upward jets and sprays. In all cases there has been some substantial clearance between the spring seat and the siphon tube, needed for purposes of manufacture and servicing, and through this clearance space there has also been a substantial upward jetting and spraying of beer at high inflow rates. In all cases, too, beer tended to issue from the holes in the cylindrical spring retainer wall with a certain amount of splattering and spraying.
Attempts have been made to minimize spraying, jetting and turbulence during the initial stages of filling at high flow rates by modifying the geometry of the holes in the cylindrical spring retainer wall. These efforts have resulted in no more than insignificant improvement.
Since the flow of beer upwardly between the spring retainer and the siphon tube is mainly along the cylindrical spring retainer wall, an attempt has been made to control upward jetting and spraying in one widely used keg valve assembly by so forming the spring seat at the axially inner end of the spring retainer as to dead-end the axial flow at that point and thus force the incoming beer out through the holes in the spring retainer wall. With this arrangement, however, there necessarily remained a clearance space around the siphon tube, and much of the flow along the cylindrical wall was simply diverted radially inwardly to this outlet, from which it issued as a strong upwardly directed jet. The arrangement thus provided only a minor decrease in the time required for filling a keg.
The present invention takes an approach to the problem that is essentially the opposite of the one just described. It begins from the premise that a strong axially upward flow along the cylindrical spring retainer wall is inevitable at high inflow rates and that little or nothing can be gained by attempting to block or suppress that flow at the axially inner end of the spring retainer in the hope of converting it to a static pressure that will compel outflow through the holes in the cylindrical spring retainer wall. Instead, the present invention contemplates a controlled debouchment at the inner end of the spring retainer whereby turbulence is minimized and whereby the debouched liquid is so directed that jetting and spraying are suppressed as soon as the level of beer in the keg has risen to slightly above the axially inner end of the spring retainer, so that a reduced inflow rate need be maintained for only a few seconds and filling can thereafter proceed at the maximum rate available from the filling equipment.